182 
Notes . 
of the wings permit the same freedom of movement, and their limbs, 
concave or hooked at the base, interlock with the keel : in Pelargonium 
rapaceum the wings are abruptly narrowed into a flexible claw and 
the concave base of the limb overlaps the keel in its lower part, so 
that depression of the wings may cause depression of the keel. The 
mechanism is faulty owing to a want of sufficient rigidity in the 
petals ; but the resemblance in arrangement is most striking. 
As the bud opens, it assumes a horizontal position, and the sepals 
become completely reflexed, the last to bend being the dorsal sepal. 
When these are out of the way, the two . dorsal petals bend below 
the middle, assuming the position of the standard of a Papilionaceous 
plant, and the flower is ready for insect-visits. One day is passed in 
this the male condition, in which a slight depression of the keel causes 
the upturned dehiscing anthers to be exposed; at the end of it the 
anthers fall from the open slightly emarginate tip of the keel. On 
the next day the flower is neutral. On the third day the five stigmas 
are enabled by the elongation of the style to expand at the tip of the 
keel, where, some thirty hours before, the pollen was partly exposed. 
For three or more days the flower, if unfertilized, persists in this 
female condition, often losing, however, some of the Papilionaceous 
appearance by a displacement of the wings. In withering, the sepals 
return to the position they occupied in the bud. 
At night the open flower is directed downwards by a nutation 
of the upper part of the pedicel ; and this at the end of the male 
stage appears to facilitate the falling away of the dehisced anthers. 
The dimensions of the parts of the flower are as follows : — posterior 
sepal iomm.X2|, lateral 9x14, anterior 10x2; posterior petals 
15x3, the claw being 5-6 mm. long; wings 12x3, the claw being 
1 4 mm. long; keel n mm. long and 2 mm. deep (i. e. 4 mm. wide 
if flattened out), its claw equalling those of the wings ; tube of the 
stamens 4 mm. long; spur (nectary) 18-20 mm. long and very 
narrow. These measurements show the zygomorphy of the flower, 
which appears to be specially adapted to the visits of butterflies. 
In structure and mechanism the flower is certainly most suggestive 
of the Papilionaceae ; and noting its imperfections — viz. want of 
rigidity in the limbs and of firm interlocking between the wings and 
keel, failure of the calyx to support the wings and keel necessarily 
weak at the base, and the imperfect concealment of the sexual organs 
when the keel is not depressed — we perhaps get a glimpse of a stage 
